This invention relates to a novel magnetic material which is of cermet type comprising as essential components at least one ferromagnetic metal, namely, iron, cobalt and/or nickel, and an oxide ceramic.
A group of amorphous alloys such as Fe.sub.40 Ni.sub.40 P.sub.14 B.sub.6, Fe.sub.80 B.sub.20 and Fe.sub.78 Mo.sub.2 B.sub.20 are typical examples of conventional magnetic materials large in hardness and high in saturation magnetic induction. With respect to Fe.sub.40 Ni.sub.40 P.sub.14 B.sub.6 by way of example, saturation magnetic induction is 7800 gauss, specific resistance is 180.times.10.sup.-6 .OMEGA.cm, Vickers hardness is 640 Hv, and magnetostriction constant is 31.times.10.sup.-6.
These amorphous magnetic materials can be produced by rapid freezing of molten alloy composition, deposition by vacuum evaporation onto a cooled substrate, electrodeposition or electroless plating. Among these techniques, the most prevailing one is the rapid freezing method in which a molten alloy is instantaneously freezed by, for example, dropping the molten alloy onto a cooled body of cupper so that the molten alloy may solidify with the maintenance of liquid state arrangement of its atoms. In practice this method is classified into (a) gun method, (b) piston-and-anvil method, (c) torsion-catapult method, (d) centrifugal freezing method and (e) rolling method. However, the methods (a), (b) and (c) can provide the magnetic alloy only in the form of powder or films 1 to 50 .mu.m in thickness and indefinite in shape. The products of the methods (d) and (e) are limited to ribbons 1 .mu.m to 10 mm in width and 10 .mu.m to 1 mm in thickness and, therefore, need to be subjected to machining.
Some of amorphous magnetic alloys such as Fe.sub.80 B.sub.20 are produced by sputtering, but inconveniently there is the need of cooling the subtrate with water to 60.degree.-100.degree. C. to avoid excessive heating of the deposited alloy.
Besides difficulties and troublesomeness in the production, these amorphous magnetic materials have a common disadvantage that annealing of these materials causes increase in coercive force due to relatively low crystallization temperatures and, therefore, are unsuitable for magnetic devices which undergo heating either during fabrication or in operation. Furthermore, these magnetic materials are not yet fully satisfactory in saturation magnetic induction values.